Process and composition for use in munitions containing white phosphorus

ABSTRACT

A PROCESS WHEREIN A SOLIDIFIED COMPLEX OF WHITE PHOSPHORUS AND POLYESTER IS DISPERSED IN A POLYURETHANE MATRIX CONCURRENT WITH OR PRIOR TO SHAPING IN THE FORM OF A MUNITION.

Patented Sept. 26, 1972 PROCESS AND COMPOSITION FOR USE IN MUNITIONS CONTAINING WHITE PHOSPHORUS Jean P. Picard, Morristown, and H. William Voight, Jr.,

Stanhope, N.J., assignors to the United States of Amerion as represented by the Secretary of the Army No Drawing. Filed July 24, 1970, Ser. No. 58,183

Int. Cl. (306d 1/08 US. Cl. 14929 17 Claims ABSTRACT OF THE DISCLOSURE A process wherein a solidified complex of white phosphorus and polyester is dispersed in a polyurethane matrix concurrent with or prior to shaping in the form of a munition.

The invention described herein may be manufactured, used and licensed by or for the Government for Governmental purposes without the payment to us of any royalties thereon.

This invention relates to a method of processing munitions containing white phosphours. More particularly, this invention relates to an improved method of safety casting white phosphorus in an artillery shell.

In the past, the munition art recognized that to have a consistently reproducible trajectory and therefore a greater degree of accuracy, it was necessary to prevent movement of the payload within the shell during flight. This was an especially troublesome problem with respect to shells containing white phosphorus because of its relatively low-melting-point. Above 44 C. the solidified mass tends to liquefy and, as a result, is then responsive to forces of flight, causing movement Within the shell which affects the ballistic stability and ultimately, the accuracy of the round involved.

Attempts were made to overcome this problem, one of which was to encapsulate particles of white phosphorus within a solidified matrix of plastic material. The latter approach accomplished its purpose and flight stability was maintained in shells containing white phosphorus even though stored for extended periods of time at relatively high temperatures. However, there was one difliculty inherent in the process of encapsulating white phosphorus. This difiiculty was the requirement of preparing, processing and generally working with fine particles of a highly dangerous material. Special techniques were necessary to provide the proper size of white phosphorus for encapsulation. These techniques, in many cases, required the use of a blanket of nitrogen gas as a precautionary measure against fire during processing. The difiiculty with this measure is that one never has complete assurance with regard to safety when working with a blanket of nitrogen gas. A person of long-term experience is required, as a practical matter, because the technique of operating and using a nitrogen blanket is highly complex, requires special equipment, and if not properly provided, disastrous results may be obtained.

The aforesaid disadvantages of the art are substantially overcome by the present invention, hereinafter described, with particular reference to the use of white phosphorus in artillery shells at elevated temperatures.

We have now invented a process wherein the absolute requirement for safety is maintained in a simplified manner while the white phosphorus, in bulk form, is uniformally dispersed into a plastic matrix thereby maintaining the flight stability of the round.

It is an object of this invention to provide an improved method of processing white phosphorus for use in munitions.

A further object is to provide an improved process for the safe handling of white phosphorus during munition manufacture having ease in use under a wide variety of conditions.

Another object is to provide an improved process for use in the casting of white phosphorus having enhanced safety.

Broadly, the process of this invention includes the forming of a solidified complex from white phosphorus and a liquid polyester resin, followed by the dispersion of such solidified mass in a liquid system, which consists of a polyurethane prepolymer and a curing agent, to form a fluid suspension, the latter being shaped into the form of a solidified payload of an artillery shell.

More specifically, in the process of this invention, white phosphorus is melted in an excess of a liquid polyester resin. The temperature of the system is then lowered below the melting point of the white phosphorus thereby forming a solidified complex of white phosphorus and polyester in an excess of the latter chemical. The solidified mass is then transferred to a liquid prepolymer system of polyurethane which is then cured to form a solidified mass of the white phosphorus complex embedded in a polyurethane matrix. The latter stage of the process may be carried out concurrent with or prior to the shaping of resulting mass in the form of a shell.

In the initial phase of the process, a solid piece of white phosphorus, which is maintained under a blanket of water, is transferred by pouring to a beaker containing a liquid polyester resin. The white phosphorus will then gravitate to the liquid polyester in the lower portion of the beaker and the water will form a separate upper phase. Further, the liquid polyester which is essentially hydrophobic will force the water off the surface of the solid and the latter will be essentially moisture-free and dry. At this point, the water may be decanted from the system in complete safety.

The liquid unsaturated polyester resins which may be utilized in the foregoing phase of the process may be found defined in the Military Standardization Handbook titled Plastics MIL-HDBK700 (MR), dated Nov. 1, 1965. The polyester may be present in an amount between 5 and 33 percent by weight based on the weight of the white phosphorus present in the system. Preferably, an amount between 9 and 10 percent has been found to give satisfactory results in this phase of the process. An amount below 5 percent should not be utilized in this initial stage because of safety. It has been found that to be acceptable in the plant or laboratory, the solid phosphorus pieces must at least be covered by the liquid polyester. Further below 5 percent, the system is inoperative due to the fire hazard inherent in the use of white phosphorus. It is also undesirable and economically impractical to go above 35 percent because the final cast will be deficient in smokeproducing properties as a result of the inclusion of an excessive amount of inert material and the physical properties needed in the final cast would be lacking.

After the water is removed from the system, the temperature of the polyester phase is increased to a point above the melting point of the pieces of white phosphorus contained therein, which is about 44 C., while the liquid polyester resinous phase containing the solid phosphorus is agitated on a continuous basis. This heating operation is not hazardous and may be simply carried through with assurance that it fully fulfills all the requirements of safety in the plant or laboratory. In theory, the initial phase of the formation of an inclusion-complex has taken place between the white phosphorus and the polyester liquid. However, the temperature of the system should never be raised above 71 C. because of safety requirements. After a uniform solution is obtained, the temperature of the system is decreased to a point below the melting-point of the white phosphorus and a solidified mass is formed in an excess of the polyester liquid. The solid material represents an inclusion-complex of white phosphorus and polyester resin. In theory, the molecules of the polyester component are caged or contained within the crystal lattice or framework of the white phosphorus component. The solidified mass of these two components are now in the form of globules, or beads depending on the mode of agitation of the system.

The solid inclusion-complex phase of the system may now be removed from the liquid phase by any of the methods known in the art. This may be accomplished in complete safety because the solid complex will not ignite in air even though it contains white phosphorus. It has been found by analytical extraction that the white phosphorus cages or takes into its lattice approximately 9 percent of the polyester component.

In the second phase of the process, the mass of the solid-complex may now be dispersed with stirring into the isocyanate-terminated polyurethane prepolymer system either with or without a polyol curing agent such as castor oil. The polyurethane prepolymer solution is compatible with and has an affinity for the polyester component of the solidified complex and no difiiculty will be encountered in dispersing the solid complex in the polyurethane solution. The resulting solution from the above procedure is a suspension of the inclusion-complex in the polyurethane prepolymer system.

Preferably, the polyurethane-producing system consists of a liquid polymeric diisocyanate, such as the reaction product of 2,4-tolylene diisocyanate and 1,4-butylene oxide polyglycol, accompanied by a suitable curing agent such as a liquid polyol. The latter may be castor oil or meltable hydrogenated castor oil. Highly acceptable results have been achieved with such a polyurethane system.

However, it has also been found that the final cast product may be strongly influenced by the choice of isocyanate and hydroxy components utilized in this phase of the process. It is preferred to utilize symmetrical diisocyanates and glycols in the process because they are useful in the production of elastomers of high modulus. These include diisocyanates such as naphthylene-l, S-diisocyanate; phenylene-l, 4-diisocyanate; and diphenylmethane-4,4-diisocyanate. The symmetrical glycols which are of use include 1,4-butanediol; 1,6-hexanediol; p-bis([3- hydroxyethoxy) benzene and 1,5-bis(fl-hydroxyethoxy) naphthalene. Other materials which may be used include esters of ricinoleic acid having an equivalent weight of 200 and containing an isocyanate content of 21 percent. Such materials may be found described in US. 3,483,150.

The polyurethane-producing system should be present in an amount between and 50 percent by weight based on the weight of the solidified complex. If an amount below 10 percent is used, the required physical characteristics of the final product will be lacking. However, if an amount above 50 percent is present, the final cast product will be deficient in its smoke-producing properties and therefore unacceptable as a marker for military use. Highly acceptable results were achieved with a system containing about 25 percent of a polyurethane-producing material.

Further, it is preferred to have a stoichiometric balance of curing agent to the polyurethane prepolymer systern to achieve the best results in terms of the physical properties of the final cast and for latitude in time of handling.

In the final phase of the process, the fluid suspension producted in accordance to the above description is shaped by being transferred to a mold such as a shell. However, there are alternates to this procedure. For instance, the polyurethane prepolymer solution with curing agent may be initially added to the shell followed, in sequence, by the solid inclusion-complex or the curing agent may be added just prior to capping. In either situation, the system will progress from a satisfactory fluid state to a solid state at room temperature within two weeks. This latter state may be achieved in an accelerated manner by the application of heat below about 71 C.

EXAMPLE 1 A 150 ml. beaker containing 26.1 grams of white phosphorous under a blanket of mls. of water was emptied into a second beaker containing 2.7 grams of a liquid unsaturated polyester resin, the latter being made from maleic anhydride and propylene glycol. The upper layer of water was removed by decantation. Heat was then applied to the second beaker until the temperature of the liquid polyester portion reached 46 C. and the contents were continually stirred until the ingredients formed a well distributed suspension. The latter fluid was then poured into a silicone mold which had been previously wet with the liquid polyester. The mold had a channel of A of an inch diameter. The suspension was allowed to solidify into strands and the excess polyester fluid was poured off. The resulting strands were then cut in the form of grains having lengths of approximately A of an inch. Then 26.1 grams of these grains were transferred to the cavity of an empty 40 mm. shell and 7.9 grams of the polyurethane liquid system was then poured with stirring into the same shell cavity. The latter system consisted of 5.3 gms. of the reaction product of 2,4- tolylene diisocyanate and 1,4-butylene oxide polyglycol accompanied by 2.6 gms. of castor oil. After a mild agitation, the shell was capped with 0.85 gram of the above polyurethane liquid, sealed in the conventional manner and cured for 2 days at room temperature. Upon analysis, the resulting composition was found to be 71.2 percent white phosphorus, 7.3 percent polyester, and 21.5 percent polyurethane, all percentages being by weight of the total composition.

EXAMPLE 2 Balls of the solidified complex containing white phosphorus and polyester were formed in the manner set forth in Example 1 except that, in this case, a polyethylene mold was used which had ball-like depressions of A of an inch each. Also, the amount of materials utilized in the procedure were 30.3 gms. of white phosphorus covered by an excess of the polyester liquid. Further, the polyester utilized in this case was made from an unsaturated fumaric acid and ethylene glycol. Also, the temperature of the polyethylene mold was lowered by the application of Dry Ice. After the suspension solidified, the excess liquid was poured ofl. At room temperature, 27.0 gms. of the latter balls were then added to a vessel containing 4.7 gms. of the polyurethane prepolymer solution set forth in Example 1. After about 5 minutes of mild stirring, 2.3 gms. of castor oil were added to the beaker and the agitation was continued. The resulting suspension was transferred to the cavity of a 40 mm. shell and the shell was capped with 1 gm. of the polyurethane liquid system, sealed in a conventional manner and cured at 40 C. for 16 hours. Upon analysis, the resulting composition was found to be 73 percent while phosphorus, 7 percent polyester and 20 percent polyurethane.

Results Upon actual firing, the composition of the shell prepared in accordance with the procedure of Example 1 formed a spectacular plume burst accompanied by scattered pieces of white phosphorus for anti-personnel action. However, upon firing in the same manner, the composition of the shell prepared by the procedure of Example 2 formed a typical smoke pot for marking lasting well over 3 minutes.

It has also been found that a cast prepared in accordance with the process of this invention exhibits no shrinkage in the shell upon cure and is firmly adhered or casebonded to the inner shell wall. As a result, shells containing such casts may be subjected to a cycle of temperature from 71 C. to 50 C. without exhibiting shrinking or independent spinning of the cast upon firing of the shell. There is no loss in the physical properties of the cast upon aging and the mechanical strength of the cast is maintained even though the shell may be stored for as much as 24 months at 71 C. Further, the dimensional stability of the cast is assured even though subjected to heat as a result of the embe'dment of the white phosphorus in the polyurethane matrix. And, as heretofore stated, no movement of the liquid portion occurs above the melting point of white phosphorus and this allows the shell to land in the area calculated.

It is evident, as heretofore stated, that the process of this invention is a simplified approach to the problem of safety in dispersing white phosphorus into a plastic-matrix in order to ultimately achieve flight stability of the round into which it is cast.

We claim:

1. In the process of preparing white phosphorus for use in an artillery shell, the improvement comprising:

forming a solidified complex of said white phosphorus and a liquid polyester,

dispersing said solidified complex in a liquid system consisting of a liquid polyurethane prepolymer and a curing agent to form a fluid suspension, and shaping and curing said resulting fluid suspension.

2. The process of claim 1 wherein said forming is accomplished by melting said white phosphorus in an excess of polyester liquid followed by lowering the temperature below the melting point of said white phosphorus to form a solidified complex in said excess of liquid polyester.

3. The process of claim 1 wherein said liquid polyester is formed from an unsaturated acid and glycol,

said unsaturated acid selected from the group consisting of maleic acid and fumaric acid, and

said glycol selected from the group consisting of ethylene glycol and propylene glycol.

4. The process of claim 1 wherein said polyurethane prepolymer is the reactions product selected from the group of reactants consisting of:

(A) 2,4-tolylene diisocyanate and 1,4-butylene oxide glycol;

(B) naphthylene-1,5-diisocyanate and 1,4-butanediol;

(C) naphthylene-1,5-diisocyanate and 1,6-hexanediol;

(D) naphthylene-1,5-diisocyanate and p-bis(fl-hydroxyethoxy) benzene;

(E) naphthylene 1,5 diisocyanate and 1,5-bis(fl-hydroxyethoxy naphthalene;

(F) phenylene-1,5-diisocyanate and 1,4-butanediol;

(G) phenylene-1,5-diisocyanate and 1,6-hexanediol;

(H) phenylene-1,5-diisocyanate and p-bis(;3-hydroxyethyloxy) benzene;

(I) phenylene-l,S-diisocyanate and l,5-bis(,8-hydroxyethoxy)naphthalene;

(J) diphenylmethane-4,4'-diisocyanate and 1,4-butanediol;

(K) diphenylmethane-4,4-diisocyanate and 1,6-hexanediol;

(L) diphenylmethane-4,4'-diisocyanate and p-bis(fl-hydroxyethoxy) benzene; and

(M) diphenylmethane-4,4'-diisocyanate and 1,5-bismhydroxyethoxy)naphthalene.

5. The process of claim 1 wherein said curing agent is castor oil.

6. The process of claim 1 wherein said polyester is present in the forming stage in an amount between 5 and 33 percent by weight based on the weight of said white phosphorus.

7. The process of claim 1 wherein said polyester is present in the forming stage in an amount between 9 and 10 percent by weight based on the weight of said white phosphorus.

8. The process of claim 1 wherein said solidified complex contains approximately 9 percent by weight of said polyester.

9. The process of claim 1 wherein said polyurethane producing system is present in the dispersion stage in an amount of about 10 and 50 percent by weight based on the weight of the solidified complex.

10. The process of claim 1 wherein said polyurethaneproducing system is present in the dispersion stage in an amount of about 25 percent by weight based on the weight of the solidified complex.

11. A composition for use in a munition consisting essentially of:

A dispersion of (1) A solid, particulate inclusion complex of white phosphorous and a polyester resin containing about 65-95% phosphorous and about 5-35 of said polyester, in

(2) 10-50% by weight of said inclusion complex of a liquid polyurethane prepolymer and a curing agent therefor.

12. A composition as defined in claim 11 wherein said polyurethane prepolymer is a reaction product selected from the group of reactants consisting of:

(A) 2,4-tolylene diisocyanate and 1,4-butylene oxide glycol;

(B) naphthylene-l,S-diisocyanate and 1,4-butanediol;

(C) naphthylene-1,5-diisocyanate and 1,6-hexanediol;

(D) naphthylene-1,5-diisocyanate and p-bisQB-hydroxyethoxy)benzene;

(E) naphthylene 1,5 diisocyanate and 1,5-bis(B-hydroxy)naphthalene;

(F) phenylene-l,S-diisocyanate and 1,4-butanediol;

(G) phenylene-1,5-diisocyanate and 1,6-hexanediol;

(H) phenylene-1,5-diisocyanate and p-bisQS-hydroxyethoxy)benzene;

(I) phenylene-1,5-diisocyanate and 1,5-bis(p-hydroxyethoxy) naphthalene;

(J) diphenylmethane-4,4'-diisocyanate and 1,4-butanediol;

(K) diphenylmethane-4,4'-diisocyanate and 1,6-hexanediol;

(L) diphenylmethane-4,4'-diisocyanate and p-bisQB-hydroxyethoxy)benzene; and

(M) diphenylmethane-4,4'-diisocyanate and 1,5-bis(B- hydroxyethoxy)naphthalene.

13. A composition as defined in claim 11 wherein said polyurethane prepolymer is present in the continuous phase in an amount of about 25 percent by weight based on the weight of the solidified complex.

14. A composition as defined in claim 11 wherein said curing agent is castor oil.

15. A composition as defined in claim 11 wherein said polyester is formed from an unsaturated acid and glycol.

said unsaturated acid selected from the group consisting of maleic acid and fumaric acid, and

said glycol selected from the group consisting of ethylene glycol and propylene glycol.

16. A composition as defined in claim 11 wherein said References Cited polyester is present in an amount between 9 and 10 per- UNITED STATES PATENTS cent by weight based on the w g f Said White P 2,863,751 12/1958 Ledaal 149 29 X p 3,140,210 7/1964 Sampson 149 ss 17. A composition for use in munitions consisting es- 0 3,193,422 7/1965 Buck 149-29 sentially of: 3,314,834 4/1967 Walden et a1. 149-20 X a dispersion of Seals et al. X

(1) a solid, particulate lBClUSlOn comple r of whlte CARL D. QUARFORTH: Primary Examiner phosphorous and a polyester resin containing about 10 65-95% phosphorous and about 5-35 of said poly- NELSON, Assistant Examiner ester in US. Cl. X.R. (2) 10-50% by weight of sald lIlClllSlOIl complex of a 2643 cured polyurethane polymer matrix. 

